The present invention relates to an exhaust gas purifier for removing detrimental particulates included in exhaust gases from engines used in vehicles or industries, and also relates to the operating method of the purifier.
It is known that exhaust gases particularly from diesel engines contain particulate matters, hereinafter called PMs, and that contribute to air pollution. There are two methods for eliminating PMs; one is to suppress the production of PMs by improving engines, and the other is to remove produced PMs mechanically. Belonging to the second category, the invention employs filters to trap PMs. Collected PMs are burnt to regenerate the filters. This PM-trapping-and-burning process is repeated to maintain a continuous purifying operation.
A typical example of prior art is stated in unexamined published Japanese patent application Tokukaisho 63-306218. This equipment has four filters in parallel. While at least one filter is under regeneration, the remaining filters operate to trap PMs. FIG. 6 shows a schematic plan view of this equipment.
As shown in FIG. 6, engine 103 has exhaust pipe 102, which is branched by exhaust manifolds 105 and 106. Filters 108, 109, 110, and 111 are placed at the ends of the manifolds, through valve 112 or 113. In FIG. 6, the flow of exhaust gas into filter 109 is shut off by the operation of valve 112 to cause gas burner 118, fed with oxygen through bypass 120, to eject a high-temperature gas into filter 109 to regenerate it, while the other filters 108, 110, and 111 trap PMs.
Another example in said Tokukaisho 63-306218 has three valves and one burner with four filters in parallel, where even if one filter fails to function, the remaining three filters can maintain the purifying of exhaust gases, according to the patent application.